A Strategy to Reduce the Signaling Requirements of CQI Feedback Schemes

Resource allocation in OFDMA systems involves the application of adaptive modulation/coding (AMC). AMC provides the flexibility to match the modulation-coding scheme (MCS) to each user’s channel conditions. In order to accurately determine the appropriate MCS level, full channel state information (CSI) is required by the base-station (BS). Full CSI feedback requires bandwidth to be reserved in the OFDM frame which is occupied by the users to transmit channel quality information (CQI) to the BS. Allocations and deallocations of channels reserved for CQI feedback require expensive signaling messages between the base stations and the mobile stations, and therefore should be minimized. In this paper, we show that the amount of bandwidth consumed for this type of signalling can be significantly reduced by selecting the users with the lowest average SNR to periodically feedback their instantaneous channel state information. These benefits become more evident at low values of the user velocity.